The Linux kernel futex subsystem had a vulnerability where the function need_futex_hash_allocate_default() depended strictly on the CLONE_THREAD flag for private default hash allocation. This strict dependency violated non-concurrency assumptions during mm->futex_ref per-CPU allocations, causing use-after-free bugs (e.g., KASAN slab-use-after-free in futex_hash_put) when the memory descriptor (mm) was shared in ways other than pthread semantics. The fix broadens the check to include any CLONE_VM clone except vfork, maintaining existing performance paths while preventing race conditions and reference count errors. This vulnerability is tracked as CVE-2026-52973 and has been addressed in Red Hat Enterprise Linux kernel updates for versions 9.8 and 10.2 across multiple architectures.

The vulnerability can lead to use-after-free conditions in the kernel futex subsystem, resulting in potential memory corruption. The CVSS vector indicates high impact on confidentiality, integrity, and availability (C:H/I:H/A:H), meaning exploitation could allow an attacker with local privileges to cause system crashes, data corruption, or potentially escalate privileges. No known exploits in the wild have been reported. The issue affects kernel stability and security on affected Red Hat Enterprise Linux systems.

Official patches fixing this vulnerability are available from Red Hat for Red Hat Enterprise Linux versions 9.8 and 10.2. Users should apply the kernel updates provided in advisories RHSA-2026:45114 and RHSA-2026:47040 and reboot affected systems to ensure the fix takes effect. There are no vendor advisories indicating that no action is required; therefore, applying the official updates is the recommended mitigation.